Omission of or Poor Response to Preoperative Chemoradiotherapy Impacts Radial Margin Positivity Rates in Locally Advanced Rectal Cancer

BACKGROUND: In the setting of multidisciplinary standardized care of locally advanced rectal cancer, preoperative chemoradiotherapy and total mesorectal excision have become the mainstay treatment. OBJECTIVE: This study aimed to evaluate whether the lack of preoperative chemoradiotherapy or poor response to it is associated with higher radial margin disease involvement in patients with locally advanced rectal cancer. DESIGN: This is a retrospective cohort study using a publicly available database. SETTING: Data were collected from the proctectomy-targeted National Surgical Quality Improvement Project file from 2016 to 2017. PATIENTS: A total of 1161 patients were analyzed. They were categorized into 3 groups: patients who did not receive any preoperative chemoradiotherapy (28.6%), patients who received and responded to preoperative chemoradiotherapy (41.2%), and patients who received but did not respond to preoperative chemoradiotherapy (30.2%). MAIN OUTCOME MEASURES: Response to treatment was determined by using the American Joint Committee on Cancer pretreatment and final pathological staging. Circumferential radial margin was extracted from the targeted proctectomy file. RESULTS: Disease-involved positive circumferential radial margin was found in 86 (7.4%) cases. Positive radial margin was noted in 11 of 479 patients (2.3%) who underwent preoperative chemoradiotherapy and responded to treatment, 30 of 350 patients (8.6%) who did not respond or had a poor response to preoperative chemoradiotherapy, and 45 of 332 patients (13.6%) who did not receive preoperative chemoradiotherapy (p < 0.001). Regression analysis demonstrated that patients who do not receive preoperative chemoradiotherapy or have poor response to it have 6.6 and 4 times higher chances of having a positive radial margin. LIMITATIONS: There is a risk of selection bias, unidentified confounders, and missing data despite the use of a nationwide cohort. CONCLUSIONS: Omission of indicated preoperative chemoradiotherapy or poor response to it is associated with increased risk of radial margin positivity. More efforts are needed for standardized rectal cancer care with the appropriate use of preoperative chemoradiotherapy. See Video Abstract at .